314 DR. A. E, SHIPLEY ON [ Mar. 16, 
the centre, but increasing in length as one passes outward 
(Pl. XXXVI. fig. 5). This lip is frequently drawn down over 
the tips of the mandibles. 
The only function one can suggest for the upper lip is that it 
acts as a scraping organ and it may be of use if the animal ever 
eats the epidermis of its host. 
III. The mandibles.—These are by far the most powerful of 
the mouth-parts and are very strongly chitinized. The right 
and left mandibles are not exact images of one another, as the 
tip of one always closes outside the tip of the other, and thus 
there is a slight differentiation at the apex, which is so strongly 
chitinized as to be almost black. Hach mandible is somewhat 
triangular in shape, the apex forming the tip. The articulation 
is very complex (Pl. XX XVII. fig. 6) and is mainly with the 
inner end of the powerful apodeme which runs in just in front of 
the base of the mandibles. A very powerful muscle runs into 
the external posterior angle of each mandible, the so-called 
condyle, and serves to bring it into biting contact with the other. 
The sharp shearing-edge of the mandible is admirably adapted 
for cutting off the barbules of the feathers which form the food 
of the biting-lice. 
IV. The first pair of maxille.—These are very difficult to see 
in the living animal and are best observed when in movement. 
We agree with Grosse* in describing them as lobes without any 
traces of palps. They are rounded and bear certain sete on them. 
When in motion they are shot up and pulled down between the 
mandibles and the labium or fused second maxillze; sometimes 
both are moved forward at once, sometimes they move alter- 
nately (Pl. XX XVII. fig. 7). 
V. The second pair of maxillee—These have fused together and 
form a labium of a very simple kind. There is a median plate or 
mentum in which we found no transverse furrow. This plate 
bears anteriorly a pair of one-jointed processes ending in a few 
short stiff bristles. These are called by Grosse the paraglosse, 
but, as there are a pair of minute one-jointed processes internal 
to these, it may be that they represent the palps. Whichever 
they are, they are very mobile and are constantly being divaricated 
into a position at right angles to the normal and then suddenly 
brought back again. They are obviously of use in bringing food 
to the mouth. The more median processes as well as the palps bear 
hairs. They are figured on Pls. XXXVI. & XXXVII. figs. 5 & 7. 
A median structure which we think may represent the hypo- 
pharynx is the lyriform organ, or the ‘“ cesophageal sclerite” of 
Kellogg. his median piece is strongly chitinized, deep brown 
in colour, and consequently conspicuous ; it seems to lie about in 
the same level with the first maxille, except when they are 
* Zeitschr. wiss. Zool. xlii. 1885, p. 587. 
